Electronic mail (“e-mail” or “email”), is a technique for exchanging digital messages; it typically operates across the Internet or other computer networks. “Spam” is the indiscriminate sending of unsolicited bulk messages via electronic messaging systems. Email spam is spam comprising similar or identical messages sent to a large number of recipients by email.
Email service may be provided in a number of ways. In one non-limiting example, a subscriber of a content network such as a cable television network obtains not only entertainment, but also data services, such as Internet e-mail, over the content network; some subscribers may subscribe for data services only. Furthermore in this regard, until fairly recently, the cable network was predominantly a vehicle for delivering entertainment. With the advent of the Internet and the rise in demand for broadband two-way access, the cable industry began to seek new ways of utilizing its existing plant. Pure coaxial (“coax”) cable networks were replaced with hybrid fiber networks (HFNs) using optical fiber from the head end to the demarcation with the subscriber coax (usually at a fiber node). Currently, a content-based network, a non-limiting example of which is a cable television network, may afford access to a variety of services besides television, for example, broadband Internet access, telephone service, and the like.
One significant issue for a cable operator desiring to provide digital service is the configuration of its network. Designed for one-way delivery of broadcast signals, the existing cable network topology was optimized for downstream (toward the subscriber) only service. New equipment had to be added to the network to provide two-way communication. To reduce the cost of this equipment and to simplify the upgrade of the broadcast cable for two-way digital traffic, standards were developed for a variety of new cable-based services. The first of these standards, the Data Over Cable System Interface Standard (DOCSIS® standard), was released in 1998. DOCSIS® establishes standards for cable modems and supporting equipment. DOCSIS® (Data Over Cable Service Interface Specification) is a registered mark of Cable Television Laboratories, Inc., 400 Centennial Parkway Louisville Colo. 80027, USA, and will be referred to for the remainder of this application in capital letters, without the ® symbol, for convenience.
To prevent e-mail spam (aka unsolicited bulk email), various anti-spam techniques are employed. One of the primary techniques used to prevent spam in Internet Protocol version 4 (IPv4) is “reputation.” When spam is received from a computer, its IP address is flagged as having a bad reputation. Various algorithms are used to decide how bad a reputation is before action is taken. Generally, once an IP address has a bad reputation, email from that address is blocked. Different operators may decide how bad an address can be before blocking.